VNU Journal of Science, Earth Sciences 26 (2010) 210-217
210
Impacts of climate change on water resources
in the Huong River basin and adaptation measures
Tran Thuc*
Vietnam Institute of Meteorology, Hydrology and Environment,
23/62 Nguyen Chi Thanh, Hanoi, Vietnam
Received 01 December 2010
Abstract. This study investigates impacts of climate change on water resource in the Huong River
basin in the Central Vietnam. Hydrological responses of six climate change scenarios were
calculated. Results reveal that climate change would cause significant increase in rainfall in wet
season resulting in an increase in river flow. By contrast, the decreasing trend of river flow in dry
season is a consequence of the decline of rainfall and increase of evapotranspiration under most
scenarios. Sea level rise coupled with the lowering of river stages may exacerbate salinity
intrusion. Impacts of climate change on socio-economic sectors such as agriculture, tourism,
biodiversity, fishery and aquaculture are assessed, and adaptation options for Thua Thien - Hue
Province are proposed.
Keywords: climate change, water resources, hydrological model, flood, adaptation.
1. Introduction
∗
∗∗
∗

Water management planners are now facing
considerable uncertainties on future demand
and availability of water. Climate change and
its potential hydrological effects are
increasingly contributing to this uncertainty.
With the total area of 2.830 km
2
, Huong River

Climate Change (IPCC). Changes in daily
temperature and precipitation were computed
by using Statistical Downscaling method.
The following sources of input and
boundary data were used for developing the
climate scenarios: (1) Results from Global
Circulation Models (GCM) and Ocean-
Atmospheric Global Circulation Models
(OAGCM); (2) IPCC’s global emission
scenarios and regional climate change scenarios
for South-East Asia (IPCC, 2001); (3) Past
trends of observed meteorological data from
stations of Hue, A Luoi and Nam Dong for the
last 30 - 40 years in Thua Thien - Hue
Province; and (4) Observed sea level data at
stations and analysis from the Marine Hydro-
Meteorological Center.
2.2. Hydrological/Hydraulic model application
In order to assess the potential impacts of
climate change on water resources, a set of
hydrological/hydrodynamic model, including
NAM, MIKE11 and MIKE11GIS, was
employed. Inputs for these models include daily
rainfall, and temperature data from 1961-2004,
and their projections for the period of 2010-
2100. Potential evapotranspiration were
computed for the baseline year 1990 and for the
periods 2020 - 2049 and 2071 - 2100 at A Luoi,
Nam Dong, and Hue stations.
3. Results and discussion

Sep-Nov 0.2 0.3 0.6 0.9 1.4 2.0 2.6 3.2 3.6 4.0
Year 0.2 0.3 0.4 0.6 0.8 1.0 1.2 1.6 2.1 2.6
Dec-Feb 0.2 0.3 0.4 0.6 0.8 1.0 1.2 1.5 2.0 2.5
Mar-May

0.2 0.4 0.5 0.7 0.9 1.2 1.4 1.8 2.4 3.0
Jun-Aug 0.2 0.3 0.4 0.6 0.8 1.0 1.2 1.6 2.1 2.6
A2
Sep-Nov 0.2 0.3 0.4 0.6 0.8 1.0 1.2 1.5 2.0 2.5

Results also indicate that rainfall in the
rainy season would increase by 25%. In
contrast, rainfalls in the early months of dry
season (December to February) show a decrease
by 23% for A1FI scenario. Annual rainfall has
an increasing trend in most scenarios. Table 2
shows the results of projected rainfall for
various periods.
T. Thuc / VNU Journal of Science, Earth Sciences 26 (2010) 210-217

212

Table 2. Projected change in annual and seasonal rainfall (%) in Thua Thien - Hue in 2010-2100.
Scenario

Period 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100
Year 0.5 0.9 1.5 2.5 4.0 5.7 7.3 8.7 10.0 11.0

Dec-Feb -1.0



Mar-May 0.4 0.7 1.0 1.4 1.8 2.3 2.8 3.6 4.7 5.9

Jun-Aug 0.6 1.2 1.6 2.4 3.1 3.8 4.6 6.0 7.9 9.8

A2
Sep-Nov 1.0 1.9 2.6 3.8 4.9 6.1 7.3 9.4 12.5 15.63.2. Change in river flow
Figure 1 shows period-averaged change of
annual flows relative to the baseline period
(1990) at four gauging stations for the periods
1977-2006, 2020-2049 and 2071-2100 under
the B2 scenario. From the figure, an apparent
increase in the river flow is observed; however,
the magnitude is different amongst periods and
streamflow gauging locations. Of all stations,
flow at Ta Trach increases most significantly
whereas flow at Phu Cam (downstream) has
smallest increase, 9% and almost 5%,
respectively. Results of streamflow simulation
also reveal a reduction of flow in dry season
due to the decline of rainfall.

213

3.3. Change in flooded area
Based on the MIKE11 outputs,
MIKE11GIS was employed to interpolate water
levels at all cross-sections in order to construct
a grid-based (TIN-based) water surface. The
water surface was then automatically compared
with a Digital Elevation Model (DEM) to
develop flood depth maps [1]. Table 3 shows
the predicted change of flood depth and flooded
areas in Thua Thien - Hue province for the
A1FI emission scenario compared to the flood
event in 1999.
Table 3. Flooded area in Thua Thien - Hue under A1F1 emission scenario.
Characteristics 1999 2030 2050 2070 2090 2100
Max. depth (m) 5.81 5.96 6.08 6.16 6.27 6.44
Area flooded (km
2
) 388.4 404.5 419.2 439.5 448.8 453.7
Flooded proportion (%) 7.69 8.01 8.29 8.68 8.88 8.98

It can be seen from the table that, the 1999
flood event caused an average flooded depth of
5.81m covering an area of 388.4km
2
and
accounting for 7.69% area of the entire territory
of Thua Thien - Hue Province. By the year
2030, flooded depth of almost 6m will result in

214

3.4. Change in salinity intrusion
Salinity profile was simulated by the couple
of HD and AD modules of MIKE 11 model
taking into consideration of climate change and
sea level rise. The year 2002 is selected as the
reference baseline because of the availability of
measured salinity data. Results of salinity
intrusion computation for A1FI scenario for
some cross-sections in the mainstream are
presented in Table 4. As shown in the table,
salinity concentration increases over time and
goes accordance with magnitude of sea level
rise. Result also indicates that the salinity
intrusion during dry season in the Huong River
basin due to a series of effect of sea level rise,
water reduction and increasing demand of water
users is expected to be more serious in the
future.
Table 4. Salinity concentration change at Pho Nam and Phu Cam (A1FI scenario).
Cross-section Parameter 2002 2030 2050 2070 2090 2100
Average salinity concentration (
o
/
oo
) 2 2.1 2.17 2.33 2.41 2.47
Phu Cam
Percentage (%) 0 5 8.5 16.5 20.5 23.5
Average salinity concentration (

brief summary including some representative
examples of the climate change impacts are
presented here.
Impacts on agriculture
Most of the current rice paddies would have
a high risk of flooding during wet season.
Additionally, salinity intrusion is another threat
during the dry season, especially in low-lying
areas. This may lead to a drop in food yields
which in turn threats food security.
Rice, short-term and long-term planted trees
and long-term, newly developed industrial trees
such as rubber may suffer more as the
occurrence of natural disasters is pronounced to
be more frequent. The crop patterns and
productivity are also expected to be severely
affected by climate change.
The spread and introduction of new species
and pathogens may cause an increase in animal,
livestock and crop diseases and infections.
T. Thuc / VNU Journal of Science, Earth Sciences 26 (2010) 210-217
215

Increasing amount of pesticides and chemicals
might be used to combat this, hence, resulting
in an increasing risk of pollution and danger.
Impacts on natural fisheries and aquaculture
Changes in the flow regime will affect the
itinerary of fishing boats and other ships and
fish migration/spawning routes. Changes in the

and spotted sardine. This could also restrict the
transition and interaction between the
freshwater, brackish-water and marine
ecosystems, potentially limiting the adaptation
capacity of wildlife, domestic animals and crops.
A rise in sea temperature could also affect
coastal and marine ecosystems such as coral
reefs.
Impacts on the coastal zone
The coastal zone accounts for 30% of the
area and more than 30% of the human
population of Thua Thien - Hue Province.
Climate change impacts on the coastal zone
in the province include: (1) The shrinking of
land and coastal plain due to enlarged wetland
and flooded areas in Tam Giang - Cau Hai
lagoon would exacerbate the effects of floods to
downstream of Huong River; (2) The flooding
of terrestrial ecosystems may result in the loss
of mangrove forest; (3) Eroded seashore,
decreased land under cultivation and dwindling
residential areas will adversely affect local
incomes and livelihoods, including that of
fishermen, farmers, industrial workers and
enterprises around the lagoon and downstream
of the Huong River; (4) Threats to
infrastructure and transportation networks (sea
dyke and coastal highways), irrigation and
water works which were designed and
constructed without consideration of sea level

provincial authorities and people to carefully
balance interests with respect to the protection
and the use of coastal resources and
environment for the sustainable development of
the coastal zone [2].
The ICZM strategy document was
promulgated at the national level in 2003. The
strategy of ICZM agrees with the strategy of
adaptation to climate change in the approach,
methods of implementation and objectives of
environment protection for sustainable
development. As such, the document could
serve as an appropriate basis for implementing
climate change policies and measures at the
provincial level.
At this moment, however, the process of the
preparing the ICZM strategy has not yet
considered the changes in climate as well as
their impacts on natural conditions of the study
area. Hence the study, in close consultation
with relevant provincial stakeholders, took the
initiative to integrate some climate change
adaptation proposals into important sections of
the ICZM strategy.
The following proposal has been made for
inclusion into the ICZM Strategy: (1) Raising
management capacity for ICZM in the areas
most likely affected by climate change: Raising
awareness and knowledge among community
members, local government authorities and

to minimize the severe impacts.
Integrated approaches should drive the
future research on impact assessment in order to
fulfill the sustainable development of the river
basin.
T. Thuc / VNU Journal of Science, Earth Sciences 26 (2010) 210-217
217

Acknowledgments
This study is a part of the research
supported by the Netherlands Climate
Assistance Program (NCAP) and implemented
by the Vietnam Institute of Meteorology,
Hydrology and Environment. The author is also
grateful to valuable contributions from relevant
agencies and colleagues.

References
[1] Le Nguyen Tuong, Hoang Minh Tuyen et al.,
Analyzing impacts of climate change on Huong
river flow - Focusing on Phu Vang district,
IMHEN Technical Paper, 2007.
[2] Thua Thien Hue Provincial People’s Committee,
Five year social-economic development plan,
from 2006 to 2010, 2005 (In Vietnamese).
[3] Phong Tran, Rajib Shaw, Towards an integrated
approach of disaster and environment
management: A case study of Thua Thien - Hue
province, Central Viet Nam. Environmental
Hazards 7 (2007) 271.